This is an attempt to have generic FPU enable/disable
calls similar to x86.
So that we can simplify gpu/drm/amd/display/dc/os_types.h
Also adds FPU correctness logic seen in x86.
v2:
- Added asm/fpu/api.h powerpc variant with kernel_fpu_begin/end()
and kernel_fpu_enabled() declarations
- Updated kernel_fpu_enabled as EXPORT_SYMBOL_GPL
- Got rid of macro switch for PPC in dc/os_types.h as header file
with same name as x86 is added by previous patch in the series
Anson Jacob (2):
ppc/fpu: Add generic FPU api similar to x86
drm/amd/display: Use PPC FPU functions
arch/powerpc/include/asm/fpu/api.h | 18 +++
arch/powerpc/include/asm/switch_to.h | 25 +----
arch/powerpc/kernel/process.c | 130 ++++++++++++++++++++++
drivers/gpu/drm/amd/display/dc/os_types.h | 29 -----
4 files changed, 151 insertions(+), 51 deletions(-)
create mode 100644 arch/powerpc/include/asm/fpu/api.h
--
2.25.1
- Add kernel_fpu_begin & kernel_fpu_end API as x86
- Add logic similar to x86 to ensure fpu
begin/end call correctness
- Add kernel_fpu_enabled to know if FPU is enabled
v2:
- Added asm/fpu/api.h powerpc variant with kernel_fpu_begin/end()
and kernel_fpu_enabled() declarations
- Updated kernel_fpu_enabled as EXPORT_SYMBOL_GPL
Signed-off-by: Anson Jacob <[email protected]>
CC: Christoph Hellwig <[email protected]>
CC: Rodrigo Siqueira <[email protected]>
CC: Harry Wentland <[email protected]>
CC: Christian König <[email protected]>
---
arch/powerpc/include/asm/fpu/api.h | 18 ++++
arch/powerpc/include/asm/switch_to.h | 25 +-----
arch/powerpc/kernel/process.c | 130 +++++++++++++++++++++++++++
3 files changed, 151 insertions(+), 22 deletions(-)
create mode 100644 arch/powerpc/include/asm/fpu/api.h
diff --git a/arch/powerpc/include/asm/fpu/api.h b/arch/powerpc/include/asm/fpu/api.h
new file mode 100644
index 000000000000..57308cdc65c9
--- /dev/null
+++ b/arch/powerpc/include/asm/fpu/api.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_POWERPC_FPU_API_H
+#define _ASM_POWERPC_FPU_API_H
+
+/*
+ * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
+ * disables preemption so be careful if you intend to use it for long periods
+ * of time.
+ * TODO: If you intend to use the FPU in irq/softirq you need to check first with
+ * irq_fpu_usable() if it is possible.
+ */
+
+extern bool kernel_fpu_enabled(void);
+extern void kernel_fpu_begin(void);
+extern void kernel_fpu_end(void);
+
+#endif /* _ASM_POWERPC_FPU_API_H */
diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 9d1fbd8be1c7..a9a919279f48 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -41,10 +41,7 @@ extern void enable_kernel_fp(void);
extern void flush_fp_to_thread(struct task_struct *);
extern void giveup_fpu(struct task_struct *);
extern void save_fpu(struct task_struct *);
-static inline void disable_kernel_fp(void)
-{
- msr_check_and_clear(MSR_FP);
-}
+extern void disable_kernel_fp(void);
#else
static inline void save_fpu(struct task_struct *t) { }
static inline void flush_fp_to_thread(struct task_struct *t) { }
@@ -55,10 +52,7 @@ extern void enable_kernel_altivec(void);
extern void flush_altivec_to_thread(struct task_struct *);
extern void giveup_altivec(struct task_struct *);
extern void save_altivec(struct task_struct *);
-static inline void disable_kernel_altivec(void)
-{
- msr_check_and_clear(MSR_VEC);
-}
+extern void disable_kernel_altivec(void);
#else
static inline void save_altivec(struct task_struct *t) { }
static inline void __giveup_altivec(struct task_struct *t) { }
@@ -67,20 +61,7 @@ static inline void __giveup_altivec(struct task_struct *t) { }
#ifdef CONFIG_VSX
extern void enable_kernel_vsx(void);
extern void flush_vsx_to_thread(struct task_struct *);
-static inline void disable_kernel_vsx(void)
-{
- msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
-}
-#else
-static inline void enable_kernel_vsx(void)
-{
- BUILD_BUG();
-}
-
-static inline void disable_kernel_vsx(void)
-{
- BUILD_BUG();
-}
+extern void disable_kernel_vsx(void);
#endif
#ifdef CONFIG_SPE
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 185beb290580..969096c0123c 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -75,6 +75,17 @@
#define TM_DEBUG(x...) do { } while(0)
#endif
+/*
+ * Track whether the kernel is using the FPU state
+ * currently.
+ *
+ * This flag is used:
+ *
+ * - kernel_fpu_begin()/end() correctness
+ * - kernel_fpu_enabled info
+ */
+static DEFINE_PER_CPU(bool, in_kernel_fpu);
+
extern unsigned long _get_SP(void);
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
@@ -212,6 +223,9 @@ void enable_kernel_fp(void)
unsigned long cpumsr;
WARN_ON(preemptible());
+ WARN_ON_ONCE(this_cpu_read(in_kernel_fpu));
+
+ this_cpu_write(in_kernel_fpu, true);
cpumsr = msr_check_and_set(MSR_FP);
@@ -231,6 +245,15 @@ void enable_kernel_fp(void)
}
}
EXPORT_SYMBOL(enable_kernel_fp);
+
+void disable_kernel_fp(void)
+{
+ WARN_ON_ONCE(!this_cpu_read(in_kernel_fpu));
+
+ this_cpu_write(in_kernel_fpu, false);
+ msr_check_and_clear(MSR_FP);
+}
+EXPORT_SYMBOL(disable_kernel_fp);
#else
static inline void __giveup_fpu(struct task_struct *tsk) { }
#endif /* CONFIG_PPC_FPU */
@@ -263,6 +286,9 @@ void enable_kernel_altivec(void)
unsigned long cpumsr;
WARN_ON(preemptible());
+ WARN_ON_ONCE(this_cpu_read(in_kernel_fpu));
+
+ this_cpu_write(in_kernel_fpu, true);
cpumsr = msr_check_and_set(MSR_VEC);
@@ -283,6 +309,14 @@ void enable_kernel_altivec(void)
}
EXPORT_SYMBOL(enable_kernel_altivec);
+void disable_kernel_altivec(void)
+{
+ WARN_ON_ONCE(!this_cpu_read(in_kernel_fpu));
+
+ this_cpu_write(in_kernel_fpu, false);
+ msr_check_and_clear(MSR_VEC);
+}
+EXPORT_SYMBOL(disable_kernel_altivec);
/*
* Make sure the VMX/Altivec register state in the
* the thread_struct is up to date for task tsk.
@@ -333,6 +367,9 @@ void enable_kernel_vsx(void)
unsigned long cpumsr;
WARN_ON(preemptible());
+ WARN_ON_ONCE(this_cpu_read(in_kernel_fpu));
+
+ this_cpu_write(in_kernel_fpu, true);
cpumsr = msr_check_and_set(MSR_FP|MSR_VEC|MSR_VSX);
@@ -354,6 +391,15 @@ void enable_kernel_vsx(void)
}
EXPORT_SYMBOL(enable_kernel_vsx);
+void disable_kernel_vsx(void)
+{
+ WARN_ON_ONCE(!this_cpu_read(in_kernel_fpu));
+
+ this_cpu_write(in_kernel_fpu, false);
+ msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
+}
+EXPORT_SYMBOL(disable_kernel_vsx);
+
void flush_vsx_to_thread(struct task_struct *tsk)
{
if (tsk->thread.regs) {
@@ -406,6 +452,90 @@ void flush_spe_to_thread(struct task_struct *tsk)
}
#endif /* CONFIG_SPE */
+static bool fpu_support(void)
+{
+ if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
+ return true;
+ } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
+ return true;
+ } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
+ return true;
+ }
+
+ return false;
+}
+
+bool kernel_fpu_enabled(void)
+{
+ return this_cpu_read(in_kernel_fpu);
+}
+EXPORT_SYMBOL_GPL(kernel_fpu_enabled);
+
+void kernel_fpu_begin(void)
+{
+ if (!fpu_support()) {
+ WARN_ON_ONCE(1);
+ return;
+ }
+
+ preempt_disable();
+
+#ifdef CONFIG_VSX
+ if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
+ enable_kernel_vsx();
+ return;
+ }
+#endif
+
+#ifdef CONFIG_ALTIVEC
+ if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
+ enable_kernel_altivec();
+ return;
+ }
+#endif
+
+#ifdef CONFIG_PPC_FPU
+ if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
+ enable_kernel_fp();
+ return;
+ }
+#endif
+}
+EXPORT_SYMBOL_GPL(kernel_fpu_begin);
+
+void kernel_fpu_end(void)
+{
+ if (!fpu_support()) {
+ WARN_ON_ONCE(1);
+ return;
+ }
+
+#ifdef CONFIG_VSX
+ if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
+ disable_kernel_vsx();
+ goto done;
+ }
+#endif
+
+#ifdef CONFIG_ALTIVEC
+ if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
+ disable_kernel_altivec();
+ goto done;
+ }
+#endif
+
+#ifdef CONFIG_PPC_FPU
+ if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
+ disable_kernel_fp();
+ goto done;
+ }
+#endif
+
+done:
+ preempt_enable();
+}
+EXPORT_SYMBOL_GPL(kernel_fpu_end);
+
static unsigned long msr_all_available;
static int __init init_msr_all_available(void)
--
2.25.1
Use kernel_fpu_begin & kernel_fpu_end for PPC
Depends on "ppc/fpu: Add generic FPU api similar to x86"
v2:
- Got rid of macro switch for PPC as header file with same
name as x86 is added by previous patch in the series
Signed-off-by: Anson Jacob <[email protected]>
CC: Christoph Hellwig <[email protected]>
CC: Rodrigo Siqueira <[email protected]>
CC: Harry Wentland <[email protected]>
CC: Christian König <[email protected]>
---
drivers/gpu/drm/amd/display/dc/os_types.h | 29 -----------------------
1 file changed, 29 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
index 126c2f3a4dd3..47ef434f93d8 100644
--- a/drivers/gpu/drm/amd/display/dc/os_types.h
+++ b/drivers/gpu/drm/amd/display/dc/os_types.h
@@ -51,38 +51,9 @@
#define dm_error(fmt, ...) DRM_ERROR(fmt, ##__VA_ARGS__)
#if defined(CONFIG_DRM_AMD_DC_DCN)
-#if defined(CONFIG_X86)
#include <asm/fpu/api.h>
#define DC_FP_START() kernel_fpu_begin()
#define DC_FP_END() kernel_fpu_end()
-#elif defined(CONFIG_PPC64)
-#include <asm/switch_to.h>
-#include <asm/cputable.h>
-#define DC_FP_START() { \
- if (cpu_has_feature(CPU_FTR_VSX_COMP)) { \
- preempt_disable(); \
- enable_kernel_vsx(); \
- } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) { \
- preempt_disable(); \
- enable_kernel_altivec(); \
- } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) { \
- preempt_disable(); \
- enable_kernel_fp(); \
- } \
-}
-#define DC_FP_END() { \
- if (cpu_has_feature(CPU_FTR_VSX_COMP)) { \
- disable_kernel_vsx(); \
- preempt_enable(); \
- } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) { \
- disable_kernel_altivec(); \
- preempt_enable(); \
- } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) { \
- disable_kernel_fp(); \
- preempt_enable(); \
- } \
-}
-#endif
#endif
/*
--
2.25.1
Am 21.07.21 um 06:48 schrieb Anson Jacob:
> Use kernel_fpu_begin & kernel_fpu_end for PPC
>
> Depends on "ppc/fpu: Add generic FPU api similar to x86"
>
> v2:
> - Got rid of macro switch for PPC as header file with same
> name as x86 is added by previous patch in the series
>
> Signed-off-by: Anson Jacob <[email protected]>
> CC: Christoph Hellwig <[email protected]>
> CC: Rodrigo Siqueira <[email protected]>
> CC: Harry Wentland <[email protected]>
> CC: Christian König <[email protected]>
Looks good in general, but question is what about other architectures
like ARM?
Regards,
Christian.
> ---
> drivers/gpu/drm/amd/display/dc/os_types.h | 29 -----------------------
> 1 file changed, 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
> index 126c2f3a4dd3..47ef434f93d8 100644
> --- a/drivers/gpu/drm/amd/display/dc/os_types.h
> +++ b/drivers/gpu/drm/amd/display/dc/os_types.h
> @@ -51,38 +51,9 @@
> #define dm_error(fmt, ...) DRM_ERROR(fmt, ##__VA_ARGS__)
>
> #if defined(CONFIG_DRM_AMD_DC_DCN)
> -#if defined(CONFIG_X86)
> #include <asm/fpu/api.h>
> #define DC_FP_START() kernel_fpu_begin()
> #define DC_FP_END() kernel_fpu_end()
> -#elif defined(CONFIG_PPC64)
> -#include <asm/switch_to.h>
> -#include <asm/cputable.h>
> -#define DC_FP_START() { \
> - if (cpu_has_feature(CPU_FTR_VSX_COMP)) { \
> - preempt_disable(); \
> - enable_kernel_vsx(); \
> - } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) { \
> - preempt_disable(); \
> - enable_kernel_altivec(); \
> - } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) { \
> - preempt_disable(); \
> - enable_kernel_fp(); \
> - } \
> -}
> -#define DC_FP_END() { \
> - if (cpu_has_feature(CPU_FTR_VSX_COMP)) { \
> - disable_kernel_vsx(); \
> - preempt_enable(); \
> - } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) { \
> - disable_kernel_altivec(); \
> - preempt_enable(); \
> - } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) { \
> - disable_kernel_fp(); \
> - preempt_enable(); \
> - } \
> -}
> -#endif
> #endif
>
> /*
On Wed, Jul 21, 2021 at 08:29:43AM +0200, Christian K??nig wrote:
> Looks good in general, but question is what about other architectures like
> ARM?
DRM_AMD_DC_DCN currently requires X86 || PPC64.
Maybe a good think would be to add a new KERNEL_FPU_API Kconfig symbol,
selected by x86 and powerpc (I think ppc32 should be fine too now) so
that we get these arch dependencies out of the driver.
> +
> +/*
> + * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
> + * disables preemption so be careful if you intend to use it for long periods
> + * of time.
> + * TODO: If you intend to use the FPU in irq/softirq you need to check first with
> + * irq_fpu_usable() if it is possible.
Please avoid the overly lone lines comments.
> +extern bool kernel_fpu_enabled(void);
> +extern void kernel_fpu_begin(void);
> +extern void kernel_fpu_end(void);
No need for the externs.
> +/*
> + * Track whether the kernel is using the FPU state
> + * currently.
This all fits on a single line.
> +static bool fpu_support(void)
> +{
> + if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
> + return true;
> + } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
> + return true;
> + } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
> + return true;
> + }
No need for the braces, or else after a return. In fact this could
be simplified down to:
return cpu_has_feature(CPU_FTR_VSX_COMP) ||
cpu_has_feature(CPU_FTR_ALTIVEC_COMP) ||
cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE));
> + preempt_disable();
> +
> +#ifdef CONFIG_VSX
> + if (cpu_has_feature(CPU_FTR_VSX_COMP)) {
> + enable_kernel_vsx();
> + return;
> + }
> +#endif
> +
> +#ifdef CONFIG_ALTIVEC
> + if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) {
> + enable_kernel_altivec();
> + return;
> + }
> +#endif
> +
> +#ifdef CONFIG_PPC_FPU
> + if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) {
> + enable_kernel_fp();
> + return;
> + }
> +#endif
All the features are defined away if not supported (and we already rely
on that in fpu_support()). So this could become:
if (cpu_has_feature(CPU_FTR_VSX_COMP))
enable_kernel_vsx();
else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP))
enable_kernel_altivec();
else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE))
enable_kernel_fp();
Same for the disable path.
Am 21.07.21 um 08:51 schrieb Christoph Hellwig:
> On Wed, Jul 21, 2021 at 08:29:43AM +0200, Christian K??nig wrote:
>> Looks good in general, but question is what about other architectures like
>> ARM?
> DRM_AMD_DC_DCN currently requires X86 || PPC64.
And exactly that's the problem I'm noting here. At least officially AMD
claims that we support ARM and some very brave still use the hardware
together with MIPS as well.
> Maybe a good think would be to add a new KERNEL_FPU_API Kconfig symbol,
> selected by x86 and powerpc (I think ppc32 should be fine too now) so
> that we get these arch dependencies out of the driver.
Good idea.
Christian.